This was about three or four years after their conversion. The apostle knowing very well how to suit his discourse to his auditors, in this epistle makes use of a more severe and harsh address than is observable in his other epistles. The reason is, the Galatians were a less civilized people, and had already shewn the little attachment they had to their spiritual father. (Calmet)

To another gospel: which is not[2] another. That is, it is not properly another, because they pretended to be Christians, and teach the faith: and yet it was in some measure another, because changed by such teachers with a mixture of errors, particularly that all converted Gentiles were to observe the Jewish law: and in this sense, they are said to subvert, or destroy the gospel of Christ: so that the apostle hesitates not to pronounce and repeat an anathema, a curse upon all that preach any thing besides, that is, in point of religion, not agreeing with what he had taught. I cannot omit here a reflection, which St. Chrysostom makes on the 7th verse. Where are they, saith he, who condemn us (Catholics) for the differences we have with heretics? and who pretend there is no such essential difference betwixt us and them, so as to judge them excluded from the communion of the Catholic Church, out of which there is no salvation, unless perhaps through ignorance.

Let them hear what St. Paul says, that they destroyed the gospel who made any such innovations: to wit, by introducing again as necessary some of the Jewish ceremonies, even at a time when the Christians, who had been Jews, might lawfully use them, and even they who had been Gentiles. St. Paul says, this is to change and destroy the gospel; he repeats anathema against them. Let them hear, and take notice of this, who pretend that the unity of the one Catholic faith is sufficiently maintained by all Christian societies, that agreeing, as they say, in fundamentals, their faith is a saving faith: that the council of Trent, without reason, pronounced such anathemas against them: that all Catholics are uncharitable for denying them to be in the way to salvation, when they make Scripture alone, as interpreted by their private judgment, the only rule of their faith. They may as well accuse not only St. Chrysostom but also St. Paul, of uncharitableness, &c. (Witham)